The present invention relates to a head-rest arrangement, and more particularly relates to a head-rest arrangement for use in a motor vehicle seat.
It is known that if a motor vehicle is involved in a rear impact, the occupant of a seat within the vehicle may suffer from so-called “whiplash” injuries.
When a vehicle is involved in a rear impact, the chassis of the vehicle is suddenly accelerated from a stationary condition or a low speed, to a relatively high speed. The seats within the vehicle, which are typically securely fastened to the chassis, thus experience an equivalent rapid acceleration. That rapid acceleration is imparted to the parts of the occupant of the seat that are in contact with the seat; namely, the posterior and the lower part of the torso. The head of the occupant of the seat remains in its initial position, or at its initial velocity. Since the torso of the occupant of the seat has been given a substantial acceleration, the torso moves forwardly relative to the head. The neck of the occupant of the seat thus becomes distorted from its ordinary condition and is deformed to an “S”-type configuration. Finally the head is accelerated forwardly, by the force applied to it by the neck, with a simultaneous rotation about a horizontal axis. This imparts a severe strain on the neck which causes the so-called “whiplash” injuries.
It has been found that the degree of whiplash injury may be reduced if the head-rest of the vehicle seat is moved forwardly at an initial stage of a rear impact situation so that the head-rest moves into contact with the rear part of the head of the occupant of the seat. Then, as the seat is accelerated forwardly accelerating the posterior and torso of the occupant, the seat simultaneously accelerates the head of the occupant forwardly. The head moves simultaneously with the torso, thus minimising the risk of whiplash injury arising.